1. Field of the Invention
The present invention relates to an image processing apparatus.
2. Related Background Art
The magnetic disk called still video floppy disk records a still image by separately frequency modulating the luminance signal and the line-sequential color difference signal and frequency multiplexing these signals. Consequently, for obtaining an NTSC standard video signal, for example, in a reproducing apparatus, it is necessary to separate the frequency multiplexed FM signal into the luminance component and the color difference component, separately frequency demodulate these components, convert the line-sequential color difference signal into a line-simultaneous signal, and convert these components into the standard video signal.
Based on the recent advent of digital image processing technology, there is proposed a circuit structure for storing the reproduced signal in a frame memory and conducting various image signal processings such as conversion of the line-sequential color difference signal into line-simultaneous signal or conversion into the standard television signal, on said frame memory. For example there are proposed a structure for storing the reproduced luminance signal in a frame memory in a first field, then storing the reproduced (line-sequential) color difference signal in the frame memory in a second field, effecting digital signal processing on the data stored in the frame memory for obtaining luminance data and two color difference data, and converting these data into analog signals which are converted into the NTSC standard video signal by an NTSC encoder, and a structure for forming a digital video signal for display on real-time basis from the luminance data and the line-sequential color difference data stored in the frame memory, and converting said digital signal into an analog signal.
However, such conventional structures require a very large memory capacity, since all the luminance data and the line-sequential color difference data constituting an image have to be stored in the frame memory. Also a large amount of data that has to be read within a unit time requires a high-speed memory and a data bus of a large data width, so that it has been difficult to reduce the cost of the apparatus in such conventional structures.
Besides it is difficult, in the former structure, to reduce the cost, size and power consumption as there are required D/A converters and analog encoders for example of NTSC standard in three channels. Also the latter structure is very expensive as a digital processing circuit of a very high speed is required for NTSC conversion of the signal on real-time basis.
Such drawbacks exist not only in the still video image processing apparatus mentioned above but also in other various reproducing apparatus.
Also in the conventional structures, in order to compensate the time difference resulting from the difference in frequency band of the processing of luminance signal and that of color difference signal at the recording, and also to compensate the similar time difference, for example between the demodulation of luminance signal and that of color difference signal at the signal reproduction, there is usually inserted, in the luminance signal system, a delay device corresponding to the time difference between the processing circuits.
However, in the conventional structures, the use of analog delay devices providing different delay times for recording and reproduction results in the following drawbacks:
(1) A delay device capable of passing the luminance signal of a wide bandwidth is difficult to obtain, and such delay device is expensive even it is available;
(2) The use of an exclusive delay device in each of the recording circuit and the reproducing circuit increases the number of component parts, eventually leading to a difficulty in part mounting and to bulkiness of the apparatus; and
(3) A further increase in the number of component parts is unavoidable if an external image signal is to be recorded.